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000
FXUS63 KTOP 242110
AFDTOP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TOPEKA KS
310 PM CST Tue Feb 24 2015

.SHORT TERM...(This Evening through Wednesday)
Issued at 310 PM CST TUE FEB 24 2015

Local area between deep upper low over Ontario and somewhat weaker
low over Arizona. Good insolation and decent mixing allowing temps
to reach well into the 40s and break 50 in the west. Fast northwest
flow from western Canada into the Ohio Valley with water vapor
showing upper wave making southeast progress through British
Columbia and Saskatchewan.

Tonight remains quiet with slowly increasing high level cloud as the
Canadian wave enters the Northern Rockies states. Still looking like
temps will fall quickly in weak winds and clear skies. Surface low
ahead of this wave brings several hours of westerly low level winds
tonight into Wednesday morning for another warm day, but cold air
advection takes over in the late afternoon in at least northern
areas as a cold front associated with the upper wave moves in. Still
appears frontogenesis will be deep enough for a band of light precip
to develop, though amounts and timing of this is somewhat in
question. Have increased PoPs a bit thinking most northern locations
will have at more than trace amounts. The expected warmer temps
bring more of a rain and snow trend to precip.

.LONG TERM...(Wednesday Night through Tuesday)
Issued at 310 PM CST TUE FEB 24 2015

With the 12Z NAM trending slightly east with the track of the
surface wave Wednesday evening, it is looking like the precip
event may end up being relatively light. In general the model
consensus takes the better Q vector convergence and vertical
motion from eastern NEB into northern MO. While there still should
be some frontogenesis move across the area, cross sections show
the lift with this to be very short lived and not that impressive.
There does appear to be some good cold air advection early in the
evening and forecast soundings cool the column below freezing
around 00Z. Because of this think light snow will be the primary
precip type with amounts around a dusting across north central KS
to near an inch across northeast KS near the MO river. While
amounts are expected to be relatively minor, increasing north
winds may create limited visibilities while the snow is falling.
Considered whether this is enough of an impact for an advisory but
opted to hold off for now since it will likely not start snowing
until the evening once rush hour is done. Later shifts can
reconsider this.

Thursday and Friday appear to be very cold and dry as the next
arctic airmass moves through the plains. Models show 925 MB temps
around -10C for Thursday with cold air advection occurring through
the day. Because of this have trimmed a degree or two from the max
temp forecast. Friday should not be much warmer as the ridge axis
remains over the area with increasing mid and high clouds limiting
insolation. The coldest temps should occur Friday morning when
winds become there lightest as the ridge axis moves through
northeast KS. Have lows between -2 and 4 degrees Fahrenheit.

For the weekend, the biggest trend in the models has been to show
the low level cold air holding in place rather than a warm front
lifting into east central KS. This is the case in both the GFS and
ECMWF. If this is in deed the case, it makes the precip type
question a little more straight forward. Therefore I`ve trended to
the forecast more in favor of snow Saturday night into Sunday. But
since models could possibly trend back to a warmer solution, I
have not gotten rid of the mixed precip wording all together
across east central KS for Sunday. The best opportunity for
accumulating snowfall looks to be Saturday and Saturday night as a
lead shortwave moves across the forecast area from the base of the
upper trough over the southwest. The forecast continues calling
for likely POPs through this period. Have continued with some
likely POPs for Sunday as the ECMWF still brings a weak
disturbance across the area generating some QPF. However based on
the GFS there is the potential for forcing for precip to diminish
Sunday and Sunday night. The more uncertain period looks to be
Monday and Tuesday as models bring out a better defined shortwave
trough. Timing differences between the ECMWF and GFS cause some
difficulties in temps and winds by Tuesday that make it hard to
resolve precip type and temps. Because of this have not strayed
much from the model blend. Therefore there could be mixed precip
Monday and Monday evening. How fast another arctic surface ridge
moves south will have a big impact on the forecast for early next
week.

&&

.AVIATION...(For the 18Z TAFs through 18Z Wednesday Afternoon)
Issued at 1135 AM CST TUE FEB 24 2015

VFR conditions persist this afternoon with generally decreasing
westerly / northwesterly winds. Overnight, a low pressure system
begins to develop off to the northwest which will bring the winds
back to the south by late in the TAF period. Expect increasing
cloudiness, but still remaining above MVFR conditions. The snow
chance is still off to our north at all terminals until after 18Z
Wednesday.


&&

.TOP WATCHES/WARNINGS/ADVISORIES...NONE.

&&

$$

SHORT TERM...65
LONG TERM...Wolters
AVIATION...Drake